Optical discs such as a CD (Compact Disc), a DVD (Digital versatile Disc), etc. have hitherto been utilized as optical information recording mediums. Over the recent years, however, there has been a progress of developing a blue semiconductor laser of which an oscillation wavelength is on the order of 400 nm. The development of a next generation high-density optical disc such as a high-density DVD, etc. capable of recording with a higher density than the general DVD, is conducted by use of this type of blue semiconductor laser.
FIG. 12 shows an example of a now-thinkable layer structure of this type of next generation high-density optical disc.
This high-density optical disc is structured such that a recording layer 91 for recording information, a light transmitting layer 92 that transmits laser beams for recording and reproducing so that the laser beams get incident on the recording layer 91 and a lubrication layer 93 taking contact with a member on the side of an optical pickup into consideration, are stacked in this sequence on a substrate 90 composed of a resin material such as polycarbonate, etc.
The light transmitting layer 92 and the lubrication layer 93 are, when formed, irradiated with ultraviolet rays after being coated for curing. When especially the lubrication layer, etc. is formed of a material such as silicone compound, fluorine compound, etc. that exhibit radical polymerization double-bond, however, there might be a case in which a characteristic as the lubrication layer deteriorates if a reaction initiator is added thereto. In such a case, if the reaction initiator is not added, the curing is hard to be done by the irradiation of the ultraviolet rays, and the lubrication layer exhibiting having a sufficient quality can not be formed. (Refer to Japanese Patent Laid-Open Application Publication No. 4-019839, Japanese Patent Laid-Open Application Publication No. 11-162015, Japanese Patent Laid-Open Application Publication No. 7-292470, Japanese Patent Laid-Open Application Publication No. 2000-64042).